This invention relates to water heaters and especially but not exclusively to a non-pressurized type electric water heater with automatic thermostatic control suitable for domestic use.
British Patent published on 16th May 1984 under Patent No. 2079908 disclosed a water heater capable of generating hot water from room temperature to boiling temperature and also for generating steam on demand. The device comprises a water tank having a water inlet with valve means for allowing or not allowing water to enter into the tank, a one-way valve to prevent the water in the tank from flowing back into the main supply and a pressure reducing valve for ensuring that the water pressure in the inlet water pipe and in the tank does not exceed a pre-set level, means for detecting the water level in the tank, means for heating the water in the tank, means for detecting the temperature of the water in the tank, hot water outlet means disposed at the bottom of the tank, steam outlet means located at the top of the tank, and control means receiving signals from the water level detecting means, the temperature detecting means and a temperature programmer to control the pressure, temperature of water in the tank and the water inlet valve means. The water heaters thus constructed have the advantage of being energy saving, fast and practical. However, this kind of water heater cannot remove sand and other impurities in water, resulting in unfavourable influence on quality of water. Furthermore, in the course of long-term usage, the incrustation precipitated on the inner-wall of the tank will degrade the heat-efficiency and the service life of the tank. In addition, this kind of water heater is rather complicated in structure. In the applications where only hot water adjustable within a certain range of temperature is required, it is not necessary to use this kind of water heater. It is advisable to use a more simplified water heater.